Though I like the idea about the Sea Folk (see below), I'm pretty sure she will have to do with the Seanchan. Egween had a dream in LoC (p258 in my hardcover edition)in which "two ravens alighted on [Mat's] shoulders, claws sinking through his coat into the flesh beneath." In that same dream "defiance passed across [Mat's] face, and then grim acceptance." Who are the two-ravens-on-the-shoulder people? If you remember from the Seeker that met Eaginin, that mark signifies the Seanchan, and more specifically those who are property of the Imperial family. I'm pretty sure that dream foreshadows Mat's involvement with the Seanchan. I don't think he will end up as property, but that dream combines well with the DNM prophecy the snake people made and the name of the Seanchan imperial court. Don't forget that we left Mat underneath a fallen building as the Seanchan overan Ebou Dar. The DNM is Seanchan, and she's not some two-bit high lady or anything. She's connected to the empress, and somehow this will bind the Seanchan to Rand (I know that is mentioned or foreshadowed somewhere, anybody have a good page reference?). One thing is sure, however--Mat is ever the scoundrel, certainly not ready for marriage, and whoever the DNM is, it's going to be even better than Tylin when the two meet up.